LP vs HP Tanks

[rstofer]

Faber makes some mid pressure tanks (3498 psi with the plus rating, 3180 without) that are 3AA tanks, but unless you're diving with a lot of lead, you probably won't like them as they're about 15 lbs negative, full (for the 100 cu ft tank). Personally, I dive cold water and love them.

We're diving in the same places. I'll take a look at the spec sheets. My LDS doesn't stock Fabers but they're available somewhere.

I haven't heard anything bad about Worthington HP 100s in terms of failing hydro. Maybe that's why PST is out of business.

Richard

 

[Leadking]

THIS IS GREAT!!!!! Using the theories seen on this board, we can pump these babies upto 5000 psi.

 

[WD8CDH]

I think the Al 80s are a little heavy for him right now. He just turned 11.

I have been thinking about some HP 80s that might work out pretty well. I have to think about it. If he gets signed up for Peak Performance Buoyancy, I want to get rid of the aluminum tanks.

I'll keep the 50s for the pool. They are excellent for that application. I also have a doubles manifold and a set of retro bands that fit these tanks.

Richard

Faber also makes an HP71. Really nice smaller tank for kids and makes a great set of doubles later. 6.73" diameter so it makes a really trim package.

 

[WD8CDH]

<snip>

Second, and this issue was a real problem with a friend of mine last year, is that the HP tanks are usually NOT 3AA tanks and are more prone to fail hydro. My friend had 3 out of 4 PST HP100's fail hydro. (And yes, this hydro shop was familiar with the trickery spelled out in the PST bulletin).
<snip>

Another cause of PST tanks falsely failing hydro is the shop using the wrong neck adapter. They often use one for the 7/8"-14 Fire Fighter tanks which use a different o-ring and sometimes don't seal well.

 

[rstofer]

Another cause of PST tanks falsely failing hydro is the shop using the wrong neck adapter. They often use one for the 7/8"-14 Fire Fighter tanks which use a different o-ring and sometimes don't seal well.

Can you expand on this a little? I thought SCUBA tanks used a 3//4"=14 NPSM thread. I didn't realize it was anything like the 7/8"-14 thread.

Richard

 

[WD8CDH]

The PST 3500psi HP tanks used a smaller thread that is 7/8"-14 UNF thread rather than the more common 3/4" NPSM SCUBA thread. The 3442psi HP tanks use the regular 3/4" NPSM SCUBA thread.

 

[rstofer]

So it isn't a matter of using the wrong thread size on the adapter, it's a problem with the o-ring being different?

Which, I suppose, ought to bring up the question of whether or not most hydro facilities are even able to test the tank. Something to ask about...

Richard

 

[vinegarbiscuit]

Here in HI, the price for gases like oxygen (don't even think about helium!) are horrific, and industrial gas suppliers are few and far in between (which also partly explains the prices). I've seen a number of folk favoring LP tanks for their deco bottles, so they can have a full fill at 2640 psi and save themselves a bit of cash. Even my fiance is eying off 12 cf LP Faber tanks for his rebreather to save money on O2 fills.

 

[dori fish]

Rstofer,
When I was 11, i was doing resort dives and using al 80, I have actually been using them since i was 10. On the other hand I was big for my age, see if he could lift it up while the tank is attached to the bc.

 

[rstofer]

Oh, he can very probably lift them. There just isn't any point at the moment. By PADI he is limited to 40' and by family to about 30'. That Al 50 lasts quite a while at 25-30'.

I think like most cold water divers, he will trim out a little better with steel tanks. He is moving from a back-inflate BC to a BP/W so he will lose the trim weights mounted high on the BC. OTOH, he will be gaining a 5# backplate and losing some of the excess buoyancy of the floaty BC. So it remains to be seen just how it all balances out.

He currently has his weight split between integrated pockets on the BC and a harness. With the new configuration, all of the weight will be in the harness. In a perfect world, the rig would balance in such a way that he could float at the surface without the BP/W while wearing the harness. Positive tanks don't play into this scenario because they require even more weight to be mounted somewhere. Putting the weight in the harness may upset the idea of floating at the surface. The other alternatives are tank bands, weight plates or pockets on the BP/W waist belt. I would rather avoid all of them. We would be just adding weight to the rig to compensate for a poor tank selection.

It's all a balancing act.

Richard